The present invention generally relates to motors and more particularly, to a linear motor for magneto-optical disk drive or the like.
Conventionally, in a magneto-optical disk drive, a linear motor has been used for driving an optical head. The known linear motor includes a guide for guiding a movable portion having the optical head mounted thereon and a driving yoke provided separately from and in parallel with the guide such that the movable portion is displaced by a driving force produced by an electromagnetic force between the driving yoke and a coil of the movable portion. However, since the guide and the driving yoke are provided separately from and in parallel with each other, the prior art magneto-optical disk drive has such drawbacks that since the movable portion becomes greater in weight due to increase of size of the movable portion, motion characteristics of the movable portion deteriorate and that since pitching of the movable portion takes place during drive of the movable portion due to the difference in height of a line of action of the driving force applied to the movable portion and the height of a center of the guide, stable recording and reproducing operations cannot be performed.
Furthermore, in the known linear motor, the following problem arises. Namely, since a reaction (reaction force) against the driving force applied to the movable portion is reversely applied to a base of the prior art magneto-optical disk drive, a bending movement is generated in the base by this reaction force, so that a resonance mode of torsion or bending appears in the base and thus, the movable portion is adversely affected by vibrations of the resonance mode of the base. As a result, the gain margin and phase margin of the movable portion are decreased and thus, stable recording, reproducing and erasing operations cannot be performed.